Metal working and metal cutting lubrication medium and process



Feb. 3, 1970 L. A. CHAMPOUX 3,493,506

METAL WORKING AND METAL CUTTING LUBRICATION MEDIUM AND PROCESS Filed Oct. 27. 1966 A INVENTOR, 100/5 A cfl/mpoux Z/m J United States Patent 3,493,506 METAL WORKING AND METAL CUTTING LUBRICATION MEDIUM AND PROCESS Louis A. Champoux, Seattle, Wash., assignor to The Boeing Company, Seattle, Wash., a corporation of Delaware Filed Oct. 27, 1966, Ser. No. 590,073 Int. Cl. Cm 1/38; B23

US. Cl. 25231 2 Claims ABSTRACT OF THE DISCLOSURE A metal working and metal cutting lubrication composition and process wherein the composition contains an iodine and aromatic compound complex in conjunction with an oil base medium containing 20% to 70% sulfur and a rust inhibitor.

This invention relates to a lubrication medium for metals and alloys enabling cold working, forming, bur nishing and machining through reduction of the coefficient of friction on the surface of the metals and alloys. In further detail, this invention sets forth a new class of lubrication media for metals and alloys and a process for adapting said media for working operations on metals and alloys.

This invention is particularly useful for working operations on titanium and titanium alloys. The use of titanium in industry is rapidly expanding each year. Titanium has outstanding physical and chemical properties which attract the design engineer to use the material in structural parts; in particular, in structural parts where weight savings are demanded, such as the aerospace industry.

In spite of the many excellent features of titanium, such as high yield strength, ultimate strength per weight and high strength at elevated temparatures, the use of titanium metal is complicated by severe problemstitaniums lack of Wear resistance and its susceptibility to galling and seizure. These problems are particularly troublesome during any cold working and forming operations which are necessary to adapt titanium parts to fit into a structural assembly.

When one titanium part is pulled over another part (for axample, either titanium or steel) or when a titanium part is formed by another part (such as a part of steel or titanium), thin protective oxide films on the surface of the titanium are broken and asperities weld and tear, thus exposing fresh metal surfaces of the titanium. It has been shown that the chemical reactivity of such fresh metal profoundly affects the formation of satisfactory boundary lubrication for the two parts. 'Ihree general areas have been explored to reduce the coefiicient of friction of sliding titanium surfaces, including (1) altering the nature of the surface, (2) the use of a liquid lubricant, and (3) the use of a solid lubricant.

Perhaps the most successful methods of preventing galling and seizure of titanium under the above-mentioned conditions have been alterations of the surface of the titanium which alterations amount to either a coating or diffused coating of another material onto and into the titanium surface. It is immediately evident that forming operations on titanium parts could not be practically and economically conducted by altering the surface because forming operations ofter involve penetrating the whole titanium part and such surface alterations on titanium are expensive.

Liquid lubricants have been used to reduce the coefiicient of friction for sliding parts of titanium or another surface (either titanium or other material). However, the liquid lubricants olfer no reduction of friction ICC or prevention of galling or seizing when subjected to extreme pressures of forming operations.

Solid lubricants with low shear strength, such as molybdenum disulfide, graphite, boron nitride and cadmium diiodide, have been used with other metals to reduce the coefficient of sliding friction with some success. However, these materials again offer no help in forming operations.

A publication by General Electric states that a process and lubrication composition has been developed which would provide a solid film lubricant, see Wear, June 1963, 444456. This composition consisted of 1.5% iodine, 24.5% benzene and 74% SAE 10 oil. This lubrication composition was used for a series of cold working tests on .25 inch thick specimens with .50 inch diameter holes. The results demonstrated that the above lubrication composition did provide a solid film having lubrication properties on the titanium, but it was not sufficient to withstand the extreme pressures of cold working and did not completely eliminate galling.

In light of the above, it is an object of this invention to achieve lubrication media which will enable utilization of conventional cold working tools for cold working all metals and alloys including titanium and titanium alloys.

It is an additional object of the instant invention to obtain a lubrication system which reduces the thrust requirement for cold working tools to an acceptable level within the capability of the existing equipment.

It is a further object of the instant invention to obtain a lubrication system which reduces the stress factor of holes thus improving the fatigue life of metal and alloy parts when they are cold worked.

Still an additional object of the instant invention is the employment of a lubrication system in a cold working process for titanium and titanium alloy parts.

Further objects and advantages of the instant invention can be realized by those skilled in the art from a reading of the following specification, the appended claims and the drawings wherein:

FIGURE 1 depicts a cold Working tool, a titanium part with a hole to be cold worked, and a container dispensing a lubrication medium.

FIGURE 2 depicts the cold working tool in contact with the titanium part in the region of the hole to be cold worked which part has thereon a lubrication medium as set forth in the instant invention.

FIGURE 3 depicts the titanium part after the hole is cold worked and the cold working tool after the cold working process.

I have found an extreme pressure lubrication system suitable for use in forming metals and alloys which enables utilization of conventional steel cold working tools (as currently used on aluminum and aluminum alloys), which lubrication system reduces the thrust requirement for usage of such a tool and does not adversely affect the fatigue life of the metals and alloys during the cold working process. The extreme pressure lubrication system has (1) a first component of iodine or an iodine contain ing medium, (2) a second component of an aromatic carrier compound, (3) a third component of a sulfur rich oil base medium containing therein (4) a fourth component of a rust inhibitor.

An additional extreme pressure lubrication system which I have devised includes the above-mentioned four components and a fifth component of a solid lubricant material.

The components of the above-mentioned extreme pressure lubrication systems will be discussed in detail. Both systems initially have free iodine or a material capable of generating free iodine during the time that the medium is on the titanium part. The aromatic compound is thought to serve as a complexing agent for the iodine and it has been determined that a number of different compounds can be used, such as benzene, toluene, quinoline, m-xylene, chlorobenzene, nitrobenzene, 2,6-diethylaniline, diphenyl ether, anisole, ethyl benzoate, pyridine, benzene thiol and naphthalene. I have found that the oil base medium can contain various hydrocarbon oils and mixtures thereof, that is, aliphatic oils such as C H wherein x varies from about 20 to 50 and sulfur containing constituents in the oils (up to 70 weight percent of the oil), that is, aliphatic esters, sulfide compounds, free sulfur and mercaptans.

It has been found that the following rust inhibitors will give satisfactory operation in the above lubrication systems: aliphatic amines, various derivitives of aliphatic amines and heterocyclics (pyridine, quinoline and their various analogs). In addition, the fifth component of a solid lubricant can be selected from the group consisting of molybdenum disulfide, graphite, boron nitride and titanium disnlfide.

The following ranges have been successfully developed and utilized for the above-mentioned lubrication systems as preferred embodiments:

Iodine or iodine generating materialat least .1 weight percent Aromatic compoundat least 20 weight percent sulfur rich oil base mediumat least 20 weight percent and a Rust inhibitorat least 1 part per million In addition, when a solid lubricant material is added to the above components as a second extreme pressure lubrication system, at least /2 weight percent is added.

Greater utilization of the usage of the instant invention can be gained from a reference to the drawings and the following description. In FIGURE 4 a tool containing some free iron (Fe) on the work part 10' thereof is coated with a small layer of fluid 13 selected from the above-described lubrication systems above a sheet of titanium material 14 on which accumulates a small layer of fluid 13. The fluid 13 is dispensed from container means 11 by a hose means 12 onto the surface of the titanium material 14. It is felt that at this stage in the process that the iodine and aromatic compound form a complex which brings about a marked reduction in the coefficient of the friction and wear between the titanium surface and the steel tool about to cold work the titanium surface. Titanium diiodide is formed at the coated areas on the titanium part when the solution is applied, and the steel tool undergoes an oxidation process forming a magnetite coating on the steel tool (depicted by 16 in FIGURES 2 and 3).

In greater detail FIGURES 1 and 2 illustrate a further phenomenon of this invention; when the steel tool 10 is brought into contact with the solution selected from one of the above-mentioned lubrication systems, a further interaction occurs between the steel tool and the solution used in this invention. The lubrication film 13, besides providing a solid film lubricant of titanium diiodide on the surface of the titanium, reacts with the iron on the surface of the tool (any free iron in the tool available for reaction) and coats the surface of the steel working tool with a porous layer of magnetite (Fe O FIGURE 3 shows the result of a forming operation on the titanium sheet wherein sheet 14 now has an expanded hole 15 formed therein and the steel tool 10 is retracted with operative end 10 having a small coating 16 of magnetite thereon, greatly exaggerated in dimensions as shown in FIGURE 3.

The above description and figures have been set forth in exemplary form for the adaptation of the instant invention for forming operations on titanium, but it has been successfully practiced on many different materials including aluminum and aluminum alloys, ferrous alloys, stainless steel alloys, high strength steels, high speed steels, and super alloys including Rene 41, Utimet 500 and the various Hastalloy materials. It has been determined that any metallic material can be successfully formed at a lower thrust requirements through the practice of the instant invention.

Any reaction time needed between the solutions of the instant invention and the steel cold working tool can be performed before the tool is set up for the work operations of the day by soaking the tool in a solution set forth above. This soaking would allow the reaction which forms the porous magnetite layer on the steel tool. Then the practice in FIGURE 1 could involve the direct application of the solutions of the instant invention to the work sheet 14 instead of the tool 10'.

When the steel cold working tool has been reacted, it is also possible to take advantage of the magnetite film to cold work without putting any solution on the metallic sheet to be formed, thus dispensing with the step shown in FIGURE 1.

Tests were conducted to determine the length of time required to suificiently coat the cold Working tool to prevent galling (that is, react the tool to form a magnetite coating).

Soaking time, minutes: Results 1 Galling covered about 10 percent of tool. 3 Galling occurred only in streaks, about 1 percent. 12 No galling.

The chemical phenomena of the above lubrication systems will now be discussed in detail. Application of the lubrication systems selected from the above descriptions gives two basic chemical reactions. First, the lubrication system creates a film of metallic diiodide on the surface of the metal or alloy being formed, at least whenever free metal is exposed to the solution, such as during a forming operation. The lubricant in addition reacts with any iron base cold working tool and coats the tool with a dark coating analyzed to be an iron oxide at least containing some magnetite (Fe O as indicated by X-ray spectrographic studies. The reactions are as follows:

(1) Metal (available in the sheet to be formed) plus 2 I (complexed in the lubrication system) gives a metallic diiodide.

(2) Fe (available in the cold working tool) plus oxygen (available from the atmosphere) in the presence of a catalyst gives iron oxide (Fe O It is believed that the catalysts (available sulfur and a rust inhibitor) in the second reaction are very important phenomena because without the catalysts set forth above we have been unable to achieve the reaction with a cold working tool which provides lubrication during the forming operation under extreme pressures and prevents seizing and galling.

A tightly adhering film is formed on steel cold working tools (and iron containing cold working tools) when it is contacted with a metallic part having a coating of a sulfur rich oil-iodine-benzene-rust inhibitor mixture or with the mixture alone and allowed to react in air. An analysis of this film was conducted using X-ray diffraction, electron difiraction, electron microscopy and electron microprobe techniques.

The X-ray diffraction, using Debye-Scherrer powder patterns, on scrapings from the steel surface after the above reaction, indicated weak diffraction lines typical of a magnetite concentration (Fe O In the electron diffraction studies, a pure iron film was prepared by vacuum evaporation on an iron wire. The film was subsequently reacted with the oil-iodine-benzene rust inhibitor mixture and prepared for electron microscopy and diffraction analysis. The film was identified by electron diffraction to be composed of metallic iron and magnetite (E2 0 Electron micrographs of the reacted iron films showed very dense particles randomly dispersed on the film. Identification of these dense particles could not be determined.

Further analyses by use of an electron microprobe were conducted upon a polished, reacted steel surface as described above. The electron beam was moved from a nonreacted portion of the steel surface to the adhering film (reacted portion) while scanning for suspected elements. The only discontinuity found was the presence of sulfur in the film. Sulfur is present as a constituent in the oil used for the reaction mixture. As a result of the above studies, it is concluded that the film formed on the steel when reacted with the sulfur rich oil-iodine-benzene-rust inhibitor mixture in the air is magnetite (Fe O The presence of sulfur is evidently due to residue traces of oil which are retained on the surface asperities in the iron and the magnetite film after reaction.

The iron rich magnetite film has been found to be porous and very adherent to the tool. These properties are very advantageous because the pores of the film soak up and trap lubricating oils, sulfur and sulfur containing materials and any solid lubrication materials present. In this condition, as the steel forming tool is forced through the sheet being formed, the retained lubricants operate to decrease friction and prevent galling and seizing thus reducing thrust requirements for the forming operation. It must also be remembered that magnetite is an oxide having lubricating characteristics.

EXAMPLE 1 An extreme pressure lubrication system for metals and alloys was synthesized wherein was added 1.5 weight percent of iodine, 28.5 weight percent of benzene (or any other aromatic compound listed above) and 70 weight percent Vascul Base No. 5 oil. Vascul Base No. 5 is a high sulfur oil with up to 50- weight percent sulfurized fat plus hydrocarbon oil with addition of rust inhibitor in the order of parts per million. This lubricant, when applied to a metal or alloy sheet and subsequently contacted with an iron containing cold working tool, resulted in an easy formation process for the titanium sheet. A typical result was the reduction of the cold work thrust force from a normal 4600 pounds to 2500 pounds for a titanium part. This lubricant, besides creating a film of metallic diiodide on the surface of the metal or alloy, reacts with the iron base cold working tool and coats the tool with a dark coating believed to be magnetite. It requires between 3 and 15 minutes at present for the lubricant to sufliciently coat the cold working tool to prevent galling. However, this reaction can be done with the cold Working tool before the forming operation is attempted on metallic sheet.

EXAMPLE 2 A solution of 1% iodine by weight, 28% benzene by weight (or any other aromatic compound listed above), 66 weight percent Vascul Base No. 5 oil and 5% molybdenum disulfide was used to coat the surface of a metallic part to be subsequently formed. Again, a cold working tool containing free iron to react with the solution was brought in contact with the metallic part in the area of the fluid coating. Formation of the metallic part by penetration of the tool was subsequently easily accomplished. A typical result was the reduction of the cold work thrust force from a normal 4600 pounds to 2500 pounds for a titanium part. This lubrication solution, besides creating a film of metallic diiodide n the surface of the metal, reacts with the iron base cold working tool and coats the tool with a dark coating of magnetite.

EXAMPLE 3 A solution of 1 weight percent iodine, 20 weight percent benzene, 64 weight percent Mobil Met No. 27 oil and 15 weight percent titanium disulfide was used to coat the surface of a metallic part to be subsequently formed and to independently react with a steel cold working tool. Mobil Met No. 27 is a high sulfur oil with up to 5 0 weight percent sulfurized fat plus hydrocarbon oil with addition of rust inhibitor in the order of parts per million. Thereafter the cold working tool was brought in contact with the metallic part and used to expand an existing hole. Formation of the metallic part by penetration of the tool was subsequently easily accomplished. A typical result was the reduction of the cold work thrust force from a normal 4600 pounds to 2500 pounds for a titanium part. This lubrication solution, besides creating a film of metallic diiodide on the surface of the metal, reacts with the steel cold working tool and coats the tool with a dark coating of magnetite.

EXAMPLE 4 A solution of aproximately 2 weight percent iodine, 37 weight percent benzene, and 61 weight percent Mobil Met No. 29 oil was used to coat the surface of a metallic part to be subsequently cold worked and to independently react with a steel cold working tool. Mobil Met No. 29 is a high sulfur oil with up to 50 weight percent sulfurized fat plus hydrocarbon oil with addition of rust inhibitor in the order of parts per million. Thereafter the cold working tool was brought in contact with the metallic part and used to cold work an existing hole. Formation of the metallic part by penetration of the tool was subsequently accomplished. This lubrication solution, besides creating a film of metallic diiodide on the surface of the metallic part, reacts with the steel cold working tool and coats the tool with a dark coating of magnetite.

The Vascul Base No. 5 oil medium, the Mobil Met No. 27 oil and Mobil Met No. 29 oil are very poor boundary lubricants for steel sliding on titanium. They are also poor boundary lubricants for titanium sliding on titanium. The addition of molybdenum disulfide did not improve its lubricating properties. In both cases the coefficient of friction is high and severe galling occurs. The use of an aromatic compoundiodine complex-as a boundary lubricant for steel sliding on titanium provides a reduction in the coefficient of friction and galling. It appears that the iodine in the complex reacts with fresh titanium metal exposed during the cold working process to yield titanium diiodide which acts as a solid film lubricant. The titanium diiodide formed is protected from atmospheric moisture, which would cause hydrolysis by hydrophobic n 'butylbenzene. When the cold working is completed and cold worked titanium is exposed to the atmosphere, hydrolysis of the titanium diiodide occurs yielding hydrogen iodide gas. The iodine and benzene form a complex which creates the titanium diiodide surface film, a solid film lubricant. This solid film lubricant alone does prevent seizure of the titanium to the cold working tool but is not sufiicient to eliminate galling during the forming operation. The iodine and a sulfur rich hydrocarbon oil with a rust inhibitor also react with the surface of the iron base cold working tool, creating a dark hard coating of magnetite. This coating along with the titanium diiodide provides sufiicient lubricity to cold work holes in 8-1-1 titanium without any galling. It is believed that suflicient lubrication is achieved because, not only one chemical reaction takes place, but a second chemical reaction takes place due to the addition of rust inhibitors as a catalyst in the lubrication system.

It has also been found that the lubrication systems set forth above provide increased efficiency of metal removal in the machining of tough alloys. When an iron containing machining tool surface is treated with the lubrication systems of the instant invention sufiiciently to achieve a magnetite layer during machining, there is a reduction in the coefiicient of friction between the iron containing machining tool surface and the part to be machined. Further, the part being machined has a lubricating diiodide layer or a magnetite layer (if the part being machined contains iron) formed on its surface which further reduces the coeflicient of friction. It is possible to react the iron containing machining tool surface prior to the machining operation, and if the machining operation is to be lengthy, a solution of the above lubrication systems can be employed during the machining step so as to keep a magnetite layer on the machining tool and a diiodide layer on the surface of the part being machined.

The advantages of the instant invention will be readily apparent to those skilled in the art. To recite a few of the advantages, it will now be possible to use conventional steel cold working tools which most shops currently employ in cold Working aluminum parts. Before this time, expensive high grades of alloy materials were necessary tools for cold working of titanium. Further, the instant invention reduces the thrust requirement necessary for formation of titanium parts and other metallic parts which further enables the machines adapted to use conventional steel cold Working tools to be now employed in the formation of titanium and other metallic parts. A further significant contribution of the above invention is the fact that the fatigue life of titanium parts is not adversely affected during formation when the above-mentioned process and lubrication systems are employed.

While I have described and illustrated some preferred forms of my invention, it should be understood that many modifications may be made without departing from the spirit and scope of the invention, and it should therefore be understood that the invention is limited only by the scope of the appended claims.

In the claims:

1. In a metal Working and metal cutting lubricating composition containing iodine and an aromatic compound as a complex, the improvement comprising the addition of an effective amount of an oil base medium containing from 20% to 70% of a sulfur containing constituent and a rust inhibiting amount of a compound selected from the group consisting of pyridine, quinoline, and 2-6, diethylaniline.

2. A process for metal working and for metal cutting of metal and metal alloy materials comprising:

(a) applying on said materials a film of a lubrication composition of an iodine component and an aromatic component selected from the group consisting of benzene, toluene, quinoline, m-xylene, chlorobenzene, nitrobenzene, 2-6, diethylaniline, diphenyl ether, anisole, ethyl benzoate, pyridine, benzene thiol, and naphthalene in amounts sufiicient to form a complex with the iodine component, an effective amount of an oil base medium containing from 20% to of a sulfur containing constituent, and a rust inhibiting amount of a compound selecting from the group consisting of pyridine, quinoline, and 2-6, diethylaniline;

(b) contacting said metallic material in the area of said lubrication composition with an iron containing tool for a sufficient period of time to coat said tool, and

(c) subsequently working or cutting said metallic mate rial by said tool.

References Cited UNITED STATES PATENTS 1,401,760 12/1921 Claflin 252-31 3,184,409 5/1965 Furey 25258 3,228,880 l/1966 Roberts et al. 25258 OTHER REFERENCES Polar-Type Rust Inhibitors by Baker et aL, Industrial and Engineering Chemistry, pp. 2338-2347, December 1948.

Encyclopedia of Chemical Technology by Kirk, pp. 535-536, vol. 8, 1952.

Metal Working Lubricants by Bastian, 1951, McGraW- Hill Book Co., New York, pp. 11-12.

DANIEL E. WYMAN, Primary Examiner I. VAUGHN, Assistant Examiner U.S. Cl. X.R. 252-25, 47, 58 

